The present invention relates to an image data rotation apparatus for rotating image data.
A copying machine or similar apparatus uses the rotation method, wherein when rotating one-page image data, the entire page is rotated by the repeating the steps of scanning the image data in blocks each consisting of m pixels by n pixels (where m and n denote natural numbers) from the image memory; applying a 90-degree or 180-degree rotation to each block; and writing the block having been rotated, into a predetermined location of the page memory.
As shown in FIG. 7, for example, when the image data of one block consisting of four pixels by n pixels is scanned from an image memory 102, the four-pixel image data items D1 through D4 continuously arranged on one and the same line are read as the one-row image data of the block. Reading of each row is repeated n times, whereby one-block image data is read.
An image data rotation apparatus is disclosed (for example, Japanese Patent Tokkai 2000-268169) wherein the burst mode of SDRAM (Synchronous Dynamic Random Access Memory) is employed to increase the processing speed in the reading and writing of image data in blocks, as described above.
In the SDRAM burst mode, as shown in FIGS. 8(a) through 8(d), when the column address (COL) has been given after the row address (ROW), the SDRAM automatically increments the column address until the preset number of bursts (4 in this case) has been reached, thereby reading the data continuously.
In this apparatus, the one-row image data items D1 through D4 of the block are stored in the continuous addresses on the image memory 102. This is utilized to read and write the one-row image data in the SDRAM burst mode, thereby increasing data transfer speed.
In the SDRAM burst mode, the address is automatically incremented “1” by the number of bursts from the column address given in the beginning. Thus, this applies only to the cases where the image data items constituting one row of the block are arranged in the continuous addresses on the image memory. Consequently, this prior art is incapable of simultaneous processing of rotation and reduction by reading the one-row image data on the block while thinning out pixels.